The objectives of this proposal are to determine if chronic myocarditis and intramyocardial coronary artery disease are specific disease entities and to determine whether a relationship exists between these disease states and congestive cardiomyopathy. We will define the pathology and natural history of chronic myocarditis and intramyocardial coronary artery disease with the aid of endomyocardial biopsy. Endomyocardial biopsy is part of the routine diagnostic procedure for patients with cardiac disease of undetermined etiology. Patients with chronic nyocarditis will be diagnosed histologically and then included in a clinical study in process in the hospital. These patients will be rebiopsied at 1 month, 7 month and yearly intervals after diagnosis under the clinical study protocol. Patients with chronic myocarditis will be treated with steroids on a randomized basis. No patient will be biopsied solely for purposes of this proposal. We will do detailed histologic, ultrastructural and viral studies on each biopsy. We will determine whether the inflammatory process in chronic cyocarditis is ongoing and results in cardiac fibrosis? If it is related to viruses and if it can be arrested by steroid therapy? Patients with intramyocardial coronary artery disease will be identified histologically. These patients will be evaluated and followed in depth but no specific treatment will be instituted. We will do detailed structural studies on the initial biopsy and any subsequent biopsy done for clinical indications. No patient will be biosied solely for purposes of the proposal. We will characterize the vascular lesions and determine if a specific vascular lesion is associated with the clinical development of so-called ischemic or diabetic cardiomyopathy. These studies will provide new insights into the pathology and natural history of chronic myocarditis and small vessel disease and determine if these entities are related to the development of cardiomyopathy.